def test_compute_variance(self):
"""Test if the compute_variance method works"""
alphas = [0, .3, 0.5, 0.7, 1]
correct_vars = [0, 0, 0, 0.8163, 1]
for i, alpha in enumerate(alphas):
base_expecation = PauliExpectation()
cvar_expecation = CVaRExpectation(alpha=alpha,
expectation=base_expecation)
op = ~StateFn(Z ^ Z) @ (Plus ^ Plus)
cvar_var = cvar_expecation.compute_variance(op)
np.testing.assert_almost_equal(cvar_var,
correct_vars[i],
decimal=3)
def test_underlying_expectation(self, base_expecation):
"""Test the underlying expectation works correctly."""
cvar_expecation = CVaRExpectation(alpha=0.3,
expectation=base_expecation)
circuit = QuantumCircuit(2)
circuit.z(0)
circuit.cp(0.5, 0, 1)
circuit.t(1)
op = ~StateFn(CircuitOp(circuit)) @ (Plus ^ 2)
cvar = cvar_expecation.convert(op)
expected = base_expecation.convert(op)
# test if the operators have been transformed in the same manner
self.assertEqual(cvar.oplist[0].primitive,
expected.oplist[0].primitive)
def test_construction(self):
"""Test the correct operator expression is constructed."""
alpha = 0.5
base_expecation = PauliExpectation()
cvar_expecation = CVaRExpectation(alpha=alpha,
expectation=base_expecation)
with self.subTest('single operator'):
op = ~StateFn(Z) @ Plus
expected = CVaRMeasurement(Z, alpha) @ Plus
cvar = cvar_expecation.convert(op)
self.assertEqual(cvar, expected)
with self.subTest('list operator'):
op = ~StateFn(ListOp([Z ^ Z, I ^ Z])) @ (Plus ^ Plus)
expected = ListOp([
CVaRMeasurement((Z ^ Z), alpha) @ (Plus ^ Plus),
CVaRMeasurement((I ^ Z), alpha) @ (Plus ^ Plus)
])
cvar = cvar_expecation.convert(op)
self.assertEqual(cvar, expected)
def test_unsupported_operations(self):
"""Assert unsupported operations raise an error."""
cvar = CVaRExpectation(0.2)
with self.assertRaises(NotImplementedError):
cvar.compute_variance(Z)
def test_unsupported_expectation(self):
"""Assert passing an AerPauliExpectation raises an error."""
expecation = AerPauliExpectation()
with self.assertRaises(NotImplementedError):
_ = CVaRExpectation(alpha=1, expectation=expecation)